/*
** $Id: ltable.c,v 2.32.1.2 2007/12/28 15:32:23 roberto Exp $
** Lua tables (hash)
** See Copyright Notice in lua.h
*/


/*
** Implementation of tables (aka arrays, objects, or hash tables).
** Tables keep its elements in two parts: an array part and a hash part.
** Non-negative integer keys are all candidates to be kept in the array
** part. The actual size of the array is the largest `n' such that at
** least half the slots between 0 and n are in use.
** Hash uses a mix of chained scatter table with Brent's variation.
** A main invariant of these tables is that, if an element is not
** in its main position (i.e. the `original' position that its hash gives
** to it), then the colliding element is in its own main position.
** Hence even when the load factor reaches 100%, performance remains good.
*/

#include <math.h>
#include <string.h>

#define ltable_c
#define LUA_CORE

#include "lua.h"

#include "ldebug.h"
#include "ldo.h"
#include "lgc.h"
#include "lmem.h"
#include "lobject.h"
#include "lstate.h"
#include "ltable.h"
#include "lrotable.h"

/*
** max size of array part is 2^MAXBITS
*/
#if LUAI_BITSINT > 26
#define MAXBITS     26
#else
#define MAXBITS     (LUAI_BITSINT-2)
#endif

#define MAXASIZE    (1 << MAXBITS)


#define hashpow2(t,n)      (gnode(t, lmod((n), sizenode(t))))

#define hashstr(t,str)  hashpow2(t, (str)->tsv.hash)
#define hashboolean(t,p)        hashpow2(t, p)


/*
** for some types, it is better to avoid modulus by power of 2, as
** they tend to have many 2 factors.
*/
#define hashmod(t,n)    (gnode(t, ((n) % ((sizenode(t)-1)|1))))


#define hashpointer(t,p)    hashmod(t, IntPoint(p))


/*
** number of ints inside a lua_Number
*/
#define numints     cast_int(sizeof(lua_Number)/sizeof(int))



#define dummynode       (&dummynode_)

static const Node dummynode_ =
{
    {LUA_TVALUE_NIL},  /* value */
    {LUA_TKEY_NIL}     /* key */
};


/*
** hash for lua_Numbers
*/
static Node *hashnum(const Table *t, lua_Number n)
{
    unsigned int a[numints];
    int i;
    if (luai_numeq(n, 0))  /* avoid problems with -0 */
        return gnode(t, 0);
    memcpy(a, &n, sizeof(a));
    for (i = 1; i < numints; i++) a[0] += a[i];
    return hashmod(t, a[0]);
}



/*
** returns the `main' position of an element in a table (that is, the index
** of its hash value)
*/
static Node *mainposition(const Table *t, const TValue *key)
{
    switch (ttype(key))
    {
    case LUA_TNUMBER:
        return hashnum(t, nvalue(key));
    case LUA_TSTRING:
        return hashstr(t, rawtsvalue(key));
    case LUA_TBOOLEAN:
        return hashboolean(t, bvalue(key));
    case LUA_TLIGHTUSERDATA:
    case LUA_TROTABLE:
    case LUA_TLIGHTFUNCTION:
        return hashpointer(t, pvalue(key));
    default:
        return hashpointer(t, gcvalue(key));
    }
}


/*
** returns the index for `key' if `key' is an appropriate key to live in
** the array part of the table, -1 otherwise.
*/
static int arrayindex(const TValue *key)
{
    if (ttisnumber(key))
    {
        lua_Number n = nvalue(key);
        int k;
        lua_number2int(k, n);
        if (luai_numeq(cast_num(k), n))
            return k;
    }
    return -1;  /* `key' did not match some condition */
}


/*
** returns the index of a `key' for table traversals. First goes all
** elements in the array part, then elements in the hash part. The
** beginning of a traversal is signalled by -1.
*/
static int findindex(lua_State *L, Table *t, StkId key)
{
    int i;
    if (ttisnil(key)) return -1;  /* first iteration */
    i = arrayindex(key);
    if (0 < i && i <= t->sizearray)  /* is `key' inside array part? */
        return i - 1; /* yes; that's the index (corrected to C) */
    else
    {
        Node *n = mainposition(t, key);
        do    /* check whether `key' is somewhere in the chain */
        {
            /* key may be dead already, but it is ok to use it in `next' */
            if (luaO_rawequalObj(key2tval(n), key) ||
                    (ttype(gkey(n)) == LUA_TDEADKEY && iscollectable(key) &&
                     gcvalue(gkey(n)) == gcvalue(key)))
            {
                i = cast_int(n - gnode(t, 0));  /* key index in hash table */
                /* hash elements are numbered after array ones */
                return i + t->sizearray;
            }
            else n = gnext(n);
        }
        while (n);
        luaG_runerror(L, "invalid key to " LUA_QL("next"));  /* key not found */
        return 0;  /* to avoid warnings */
    }
}


int luaH_next(lua_State *L, Table *t, StkId key)
{
    int i = findindex(L, t, key);  /* find original element */
    for (i++; i < t->sizearray; i++)    /* try first array part */
    {
        if (!ttisnil(&t->array[i]))    /* a non-nil value? */
        {
            setnvalue(key, cast_num(i + 1));
            setobj2s(L, key + 1, &t->array[i]);
            return 1;
        }
    }
    for (i -= t->sizearray; i < sizenode(t); i++)    /* then hash part */
    {
        if (!ttisnil(gval(gnode(t, i))))    /* a non-nil value? */
        {
            setobj2s(L, key, key2tval(gnode(t, i)));
            setobj2s(L, key + 1, gval(gnode(t, i)));
            return 1;
        }
    }
    return 0;  /* no more elements */
}


int luaH_next_ro(lua_State *L, void *t, StkId key)
{
    luaR_next(L, t, key, key + 1);
    return ttisnil(key) ? 0 : 1;
}


/*
** {=============================================================
** Rehash
** ==============================================================
*/


static int computesizes(int nums[], int *narray)
{
    int i;
    int twotoi;  /* 2^i */
    int a = 0;  /* number of elements smaller than 2^i */
    int na = 0;  /* number of elements to go to array part */
    int n = 0;  /* optimal size for array part */
    for (i = 0, twotoi = 1; twotoi / 2 < *narray; i++, twotoi *= 2)
    {
        if (nums[i] > 0)
        {
            a += nums[i];
            if (a > twotoi / 2)  /* more than half elements present? */
            {
                n = twotoi;  /* optimal size (till now) */
                na = a;  /* all elements smaller than n will go to array part */
            }
        }
        if (a == *narray) break;  /* all elements already counted */
    }
    *narray = n;
    lua_assert(*narray / 2 <= na && na <= *narray);
    return na;
}


static int countint(const TValue *key, int *nums)
{
    int k = arrayindex(key);
    if (0 < k && k <= MAXASIZE)    /* is `key' an appropriate array index? */
    {
        nums[ceillog2(k)]++;  /* count as such */
        return 1;
    }
    else
        return 0;
}


static int numusearray(const Table *t, int *nums)
{
    int lg;
    int ttlg;  /* 2^lg */
    int ause = 0;  /* summation of `nums' */
    int i = 1;  /* count to traverse all array keys */
    for (lg = 0, ttlg = 1; lg <= MAXBITS; lg++, ttlg *= 2) /* for each slice */
    {
        int lc = 0;  /* counter */
        int lim = ttlg;
        if (lim > t->sizearray)
        {
            lim = t->sizearray;  /* adjust upper limit */
            if (i > lim)
                break;  /* no more elements to count */
        }
        /* count elements in range (2^(lg-1), 2^lg] */
        for (; i <= lim; i++)
        {
            if (!ttisnil(&t->array[i - 1]))
                lc++;
        }
        nums[lg] += lc;
        ause += lc;
    }
    return ause;
}


static int numusehash(const Table *t, int *nums, int *pnasize)
{
    int totaluse = 0;  /* total number of elements */
    int ause = 0;  /* summation of `nums' */
    int i = sizenode(t);
    while (i--)
    {
        Node *n = &t->node[i];
        if (!ttisnil(gval(n)))
        {
            ause += countint(key2tval(n), nums);
            totaluse++;
        }
    }
    *pnasize += ause;
    return totaluse;
}


static void setarrayvector(lua_State *L, Table *t, int size)
{
    int i;
    luaM_reallocvector(L, t->array, t->sizearray, size, TValue);
    for (i = t->sizearray; i < size; i++)
        setnilvalue(&t->array[i]);
    t->sizearray = size;
}


static Node *getfreepos(Table *t)
{
    while (t->lastfree-- > t->node)
    {
        if (ttisnil(gkey(t->lastfree)))
            return t->lastfree;
    }
    return NULL;  /* could not find a free place */
}


static void resizenodevector(lua_State *L, Table *t, int oldsize, int newsize)
{
    int lsize;
    if (newsize == 0)    /* no elements to hash part? */
    {
        t->node = cast(Node *, dummynode);  /* use common `dummynode' */
        lsize = 0;
    }
    else
    {
        Node *node = t->node;
        int i;
        lsize = ceillog2(newsize);
        if (lsize > MAXBITS)
            luaG_runerror(L, "table overflow");
        newsize = twoto(lsize);
        if (node == dummynode)
        {
            oldsize = 0;
            node = NULL; /* don't try to realloc `dummynode' pointer. */
        }
        luaM_reallocvector(L, node, oldsize, newsize, Node);
        t->node = node;
        for (i = oldsize; i < newsize; i++)
        {
            Node *n = gnode(t, i);
            gnext(n) = NULL;
            setnilvalue(gkey(n));
            setnilvalue(gval(n));
        }
    }
    t->lsizenode = cast_byte(lsize);
    t->lastfree = gnode(t, newsize);  /* reset lastfree to end of table. */
}


static Node *find_prev_node(Node *mp, Node *next)
{
    Node *prev = mp;
    while (prev != NULL && gnext(prev) != next) prev = gnext(prev);
    return prev;
}


/*
** move a node from it's old position to it's new position during a rehash;
** first, check whether the moving node's main position is free. If not, check whether
** colliding node is in its main position or not: if it is not, move colliding
** node to an empty place and put moving node in its main position; otherwise
** (colliding node is in its main position), moving node goes to an empty position.
*/
static int move_node(lua_State *L, Table *t, Node *node)
{
    Node *mp = mainposition(t, key2tval(node));
    /* if node is in it's main position, don't need to move node. */
    if (mp == node) return 1;
    /* if node is in it's main position's chain, don't need to move node. */
    if (find_prev_node(mp, node) != NULL) return 1;
    /* is main position is free? */
    if (!ttisnil(gval(mp)) || mp == dummynode)
    {
        /* no; move main position node if it is out of its main position */
        Node *othermp;
        othermp = mainposition(t, key2tval(mp));
        if (othermp != mp)    /* is colliding node out of its main position? */
        {
            /* yes; swap colliding node with the node that is being moved. */
            Node *prev;
            Node tmp;
            tmp = *node;
            prev = find_prev_node(othermp, mp);  /* find previous */
            if (prev != NULL) gnext(prev) = node;  /* redo the chain with `n' in place of `mp' */
            *node = *mp;  /* copy colliding node into free pos. (mp->next also goes) */
            *mp = tmp;
            return (prev != NULL) ? 1 : 0; /* is colliding node part of its main position chain? */
        }
        else    /* colliding node is in its own main position */
        {
            /* add node to main position's chain. */
            gnext(node) = gnext(mp);  /* chain new position */
            gnext(mp) = node;
        }
    }
    else   /* main position is free, move node */
    {
        *mp = *node;
        gnext(node) = NULL;
        setnilvalue(gkey(node));
        setnilvalue(gval(node));
    }
    return 1;
}


static int move_number(lua_State *L, Table *t, Node *node)
{
    int key;
    lua_Number n = nvalue(key2tval(node));
    lua_number2int(key, n);
    if (luai_numeq(cast_num(key), nvalue(key2tval(node))))  /* index is int? */
    {
        /* (1 <= key && key <= t->sizearray) */
        if (cast(unsigned int, key - 1) < cast(unsigned int, t->sizearray))
        {
            setobjt2t(L, &t->array[key - 1], gval(node));
            setnilvalue(gkey(node));
            setnilvalue(gval(node));
            return 1;
        }
    }
    return 0;
}


static void resize_hashpart(lua_State *L, Table *t, int nhsize)
{
    int i;
    int lsize = 0;
    int oldhsize = (t->node != dummynode) ? twoto(t->lsizenode) : 0;
    if (nhsize > 0)   /* round new hashpart size up to next power of two. */
    {
        lsize = ceillog2(nhsize);
        if (lsize > MAXBITS)
            luaG_runerror(L, "table overflow");
    }
    nhsize = twoto(lsize);
    /* grow hash part to new size. */
    if (oldhsize < nhsize)
        resizenodevector(L, t, oldhsize, nhsize);
    else   /* hash part might be shrinking */
    {
        if (nhsize > 0)
        {
            t->lsizenode = cast_byte(lsize);
            t->lastfree = gnode(t, nhsize);  /* reset lastfree back to end of table. */
        }
        else   /* new hashpart size is zero. */
        {
            resizenodevector(L, t, oldhsize, nhsize);
            return;
        }
    }
    /* break old chains, try moving int keys to array part and compact keys into new hashpart */
    for (i = 0; i < oldhsize; i++)
    {
        Node *old = gnode(t, i);
        gnext(old) = NULL;
        if (ttisnil(gval(old)))   /* clear nodes with nil values. */
        {
            setnilvalue(gkey(old));
            continue;
        }
        if (ttisnumber(key2tval(old)))   /* try moving the int keys into array part. */
        {
            if (move_number(L, t, old))
                continue;
        }
        if (i >= nhsize)   /* move all valid keys to indices < nhsize. */
        {
            Node *n = getfreepos(t);  /* get a free place */
            lua_assert(n != dummynode && n != NULL);
            *n = *old;
        }
    }
    /* shrink hash part */
    if (oldhsize > nhsize)
        resizenodevector(L, t, oldhsize, nhsize);
    /* move nodes to their new mainposition and re-create node chains */
    for (i = 0; i < nhsize; i++)
    {
        Node *curr = gnode(t, i);
        if (!ttisnil(gval(curr)))
            while (move_node(L, t, curr) == 0);
    }
}


static void resize(lua_State *L, Table *t, int nasize, int nhsize)
{
    int i;
    int oldasize = t->sizearray;
    if (nasize > oldasize)  /* array part must grow? */
        setarrayvector(L, t, nasize);
    resize_hashpart(L, t, nhsize);
    if (nasize < oldasize)    /* array part must shrink? */
    {
        t->sizearray = nasize;
        /* re-insert elements from vanishing slice */
        for (i = nasize; i < oldasize; i++)
        {
            if (!ttisnil(&t->array[i]))
                setobjt2t(L, luaH_setnum(L, t, i + 1), &t->array[i]);
        }
        /* shrink array */
        luaM_reallocvector(L, t->array, oldasize, nasize, TValue);
    }
}


void luaH_resizearray(lua_State *L, Table *t, int nasize)
{
    int nsize = (t->node == dummynode) ? 0 : sizenode(t);
    resize(L, t, nasize, nsize);
}


static void rehash(lua_State *L, Table *t, const TValue *ek)
{
    int nasize, na;
    int nums[MAXBITS + 1]; /* nums[i] = number of keys between 2^(i-1) and 2^i */
    int i;
    int totaluse;
    for (i = 0; i <= MAXBITS; i++) nums[i] = 0; /* reset counts */
    nasize = numusearray(t, nums);  /* count keys in array part */
    totaluse = nasize;  /* all those keys are integer keys */
    totaluse += numusehash(t, nums, &nasize);  /* count keys in hash part */
    /* count extra key */
    nasize += countint(ek, nums);
    totaluse++;
    /* compute new size for array part */
    na = computesizes(nums, &nasize);
    /* resize the table to new computed sizes */
    resize(L, t, nasize, totaluse - na);
}



/*
** }=============================================================
*/


Table *luaH_new(lua_State *L, int narray, int nhash)
{
    Table *t = luaM_new(L, Table);
    luaC_link(L, obj2gco(t), LUA_TTABLE);
    sethvalue2s(L, L->top, t); /* put table on stack */
    incr_top(L);
    t->metatable = NULL;
    t->flags = cast_byte(~0);
    /* temporary values (kept only if some malloc fails) */
    t->array = NULL;
    t->sizearray = 0;
    t->lsizenode = 0;
    t->node = cast(Node *, dummynode);
    setarrayvector(L, t, narray);
    resizenodevector(L, t, 0, nhash);
    L->top--; /* remove table from stack */
    return t;
}


void luaH_free(lua_State *L, Table *t)
{
    if (t->node != dummynode)
        luaM_freearray(L, t->node, sizenode(t), Node);
    luaM_freearray(L, t->array, t->sizearray, TValue);
    luaM_free(L, t);
}



/*
** inserts a new key into a hash table; first, check whether key's main
** position is free. If not, check whether colliding node is in its main
** position or not: if it is not, move colliding node to an empty place and
** put new key in its main position; otherwise (colliding node is in its main
** position), new key goes to an empty position.
*/
static TValue *newkey(lua_State *L, Table *t, const TValue *key)
{
    Node *mp = mainposition(t, key);
    if (!ttisnil(gval(mp)) || mp == dummynode)
    {
        Node *othern;
        Node *n = getfreepos(t);  /* get a free place */
        if (n == NULL)    /* cannot find a free place? */
        {
            rehash(L, t, key);  /* grow table */
            return luaH_set(L, t, key);  /* re-insert key into grown table */
        }
        lua_assert(n != dummynode);
        othern = mainposition(t, key2tval(mp));
        if (othern != mp)    /* is colliding node out of its main position? */
        {
            /* yes; move colliding node into free position */
            while (gnext(othern) != mp) othern = gnext(othern);  /* find previous */
            gnext(othern) = n;  /* redo the chain with `n' in place of `mp' */
            *n = *mp;  /* copy colliding node into free pos. (mp->next also goes) */
            gnext(mp) = NULL;  /* now `mp' is free */
            setnilvalue(gval(mp));
        }
        else    /* colliding node is in its own main position */
        {
            /* new node will go into free position */
            gnext(n) = gnext(mp);  /* chain new position */
            gnext(mp) = n;
            mp = n;
        }
    }
    setobj2t(L, gkey(mp), key);
    luaC_barriert(L, t, key);
    lua_assert(ttisnil(gval(mp)));
    return gval(mp);
}


/*
** search function for integers
*/
const TValue *luaH_getnum(Table *t, int key)
{
    /* (1 <= key && key <= t->sizearray) */
    if (cast(unsigned int, key - 1) < cast(unsigned int, t->sizearray))
        return &t->array[key - 1];
    else
    {
        lua_Number nk = cast_num(key);
        Node *n = hashnum(t, nk);
        do    /* check whether `key' is somewhere in the chain */
        {
            if (ttisnumber(gkey(n)) && luai_numeq(nvalue(gkey(n)), nk))
                return gval(n);  /* that's it */
            else n = gnext(n);
        }
        while (n);
        return luaO_nilobject;
    }
}

/* same thing for rotables */
const TValue *luaH_getnum_ro(void *t, int key)
{
    const TValue *res = luaR_findentry(t, NULL, key, NULL);
    return res ? res : luaO_nilobject;
}


/*
** search function for strings
*/
const TValue *luaH_getstr(Table *t, TString *key)
{
    Node *n = hashstr(t, key);
    do    /* check whether `key' is somewhere in the chain */
    {
        if (ttisstring(gkey(n)) && rawtsvalue(gkey(n)) == key)
            return gval(n);  /* that's it */
        else n = gnext(n);
    }
    while (n);
    return luaO_nilobject;
}

/* same thing for rotables */
const TValue *luaH_getstr_ro(void *t, TString *key)
{
    char keyname[LUA_MAX_ROTABLE_NAME + 1];
    const TValue *res;
    if (!t)
        return luaO_nilobject;
    luaR_getcstr(keyname, key, LUA_MAX_ROTABLE_NAME);
    res = luaR_findentry(t, keyname, 0, NULL);
    return res ? res : luaO_nilobject;
}


/*
** main search function
*/
const TValue *luaH_get(Table *t, const TValue *key)
{
    switch (ttype(key))
    {
    case LUA_TNIL:
        return luaO_nilobject;
    case LUA_TSTRING:
        return luaH_getstr(t, rawtsvalue(key));
    case LUA_TNUMBER:
    {
        int k;
        lua_Number n = nvalue(key);
        lua_number2int(k, n);
        if (luai_numeq(cast_num(k), nvalue(key))) /* index is int? */
            return luaH_getnum(t, k);  /* use specialized version */
        /* else go through */
    }
    default:
    {
        Node *n = mainposition(t, key);
        do    /* check whether `key' is somewhere in the chain */
        {
            if (luaO_rawequalObj(key2tval(n), key))
                return gval(n);  /* that's it */
            else n = gnext(n);
        }
        while (n);
        return luaO_nilobject;
    }
    }
}

/* same thing for rotables */
const TValue *luaH_get_ro(void *t, const TValue *key)
{
    switch (ttype(key))
    {
    case LUA_TNIL:
        return luaO_nilobject;
    case LUA_TSTRING:
        return luaH_getstr_ro(t, rawtsvalue(key));
    case LUA_TNUMBER:
    {
        int k;
        lua_Number n = nvalue(key);
        lua_number2int(k, n);
        if (luai_numeq(cast_num(k), nvalue(key))) /* index is int? */
            return luaH_getnum_ro(t, k);  /* use specialized version */
        /* else go through */
    }
    default:
    {
        return luaO_nilobject;
    }
    }
}


TValue *luaH_set(lua_State *L, Table *t, const TValue *key)
{
    const TValue *p = luaH_get(t, key);
    t->flags = 0;
    if (p != luaO_nilobject)
        return cast(TValue *, p);
    else
    {
        if (ttisnil(key)) luaG_runerror(L, "table index is nil");
        else if (ttisnumber(key) && luai_numisnan(nvalue(key)))
            luaG_runerror(L, "table index is NaN");
        return newkey(L, t, key);
    }
}


TValue *luaH_setnum(lua_State *L, Table *t, int key)
{
    const TValue *p = luaH_getnum(t, key);
    if (p != luaO_nilobject)
        return cast(TValue *, p);
    else
    {
        TValue k;
        setnvalue(&k, cast_num(key));
        return newkey(L, t, &k);
    }
}


TValue *luaH_setstr(lua_State *L, Table *t, TString *key)
{
    const TValue *p = luaH_getstr(t, key);
    if (p != luaO_nilobject)
        return cast(TValue *, p);
    else
    {
        TValue k;
        setsvalue(L, &k, key);
        return newkey(L, t, &k);
    }
}


static int unbound_search(Table *t, unsigned int j)
{
    unsigned int i = j;  /* i is zero or a present index */
    j++;
    /* find `i' and `j' such that i is present and j is not */
    while (!ttisnil(luaH_getnum(t, j)))
    {
        i = j;
        j *= 2;
        if (j > cast(unsigned int, MAX_INT))    /* overflow? */
        {
            /* table was built with bad purposes: resort to linear search */
            i = 1;
            while (!ttisnil(luaH_getnum(t, i))) i++;
            return i - 1;
        }
    }
    /* now do a binary search between them */
    while (j - i > 1)
    {
        unsigned int m = (i + j) / 2;
        if (ttisnil(luaH_getnum(t, m))) j = m;
        else i = m;
    }
    return i;
}


/*
** Try to find a boundary in table `t'. A `boundary' is an integer index
** such that t[i] is non-nil and t[i+1] is nil (and 0 if t[1] is nil).
*/
int luaH_getn(Table *t)
{
    unsigned int j = t->sizearray;
    if (j > 0 && ttisnil(&t->array[j - 1]))
    {
        /* there is a boundary in the array part: (binary) search for it */
        unsigned int i = 0;
        while (j - i > 1)
        {
            unsigned int m = (i + j) / 2;
            if (ttisnil(&t->array[m - 1])) j = m;
            else i = m;
        }
        return i;
    }
    /* else must find a boundary in hash part */
    else if (t->node == dummynode)  /* hash part is empty? */
        return j;  /* that is easy... */
    else return unbound_search(t, j);
}

/* same thing for rotables */
int luaH_getn_ro(void *t)
{
    int i = 1, len = 0;

    while (luaR_findentry(t, NULL, i ++, NULL))
        len ++;
    return len;
}

#if defined(LUA_DEBUG)

Node *luaH_mainposition(const Table *t, const TValue *key)
{
    return mainposition(t, key);
}

int luaH_isdummy(Node *n)
{
    return n == dummynode;
}

#endif
